Series regulator and semiconductor integrated circuit

Abstract

The series regulator has: a differential amplifier; a level shifter including a level shift transistor with a drain connected to a gate; and a source follower including an output transistor. The differential amplifier includes an amplification stage having a non-inverting input terminal for input of a reference voltage, an inverting input terminal for input of a feedback voltage, and an amplifier output terminal. The differential amplifier has a DC operation point where an error of an output voltage at the amplifier output terminal to an input voltage to the non-inverting input terminal is equal to or under a gate-source voltage of an input transistor, and a follower output terminal of the source follower is feedback-connected to the inverting input terminal. The level shifter performs a level shift to make an output voltage of the source follower coincident with the voltage at the amplifier output terminal of the differential amplifier.

What is claimed is: 
     
         1 . A series regulator comprising:
 a differential amplifier;   a level shifter including a level shift transistor with a drain connected to its own gate; and   a source follower including an output transistor,   wherein the differential amplifier includes an amplification stage having a non-inverting input terminal for inputting a reference voltage, an inverting input terminal for inputting a feedback voltage, and an amplifier output terminal,   the differential amplifier has a DC operation point at which an error of an output voltage at the amplifier output terminal to an input voltage to the non-inverting input terminal is equal to or less than a voltage between a gate and a source of an input transistor, and a follower output terminal of the source follower is feedback-connected to the inverting input terminal,   the level shifter accepts input of an output voltage from the amplifier output terminal at a source of the level shift transistor, and outputs a gate voltage thereof as a shift voltage, and   the source follower receives the shift voltage from the level shifter at a gate of the output transistor, and a source of the output transistor makes the follower output terminal.   
     
     
         2 . The series regulator according to  claim 1 , wherein the differential amplifier has a p-channel type first input transistor and an n-channel type second input transistor of which gates are commonly connected to the non-inverting input terminal,
 a p-channel type third feedback input transistor and an n-channel type fourth feedback input transistor of which gates are commonly connected to the inverting input terminal,   a first load connected to a drain of the first input transistor, and linked to a low-potential side power source, and   a second load connected to a drain of the second input transistor, and linked to a high-potential side power source, and   a common drain of the third and fourth feedback input transistors makes the amplifier output terminal.   
     
     
         3 . The series regulator according to  claim 1 , wherein the differential amplifier has a p-channel type first input transistor and an n-channel type second input transistor of which gates are commonly connected to the non-inverting input terminal,
 a p-channel type third input transistor and an n-channel type fourth input transistor of which gates are commonly connected to the inverting input terminal,   a diode-connected n-channel type fifth load transistor connected to a drain of the first input transistor, and linked to a low-potential side power source, and   a diode-connected p-channel type sixth load transistor connected to a drain of the second input transistor and linked to a high-potential side power source, and   a common drain of the third and fourth feedback input transistor makes the amplifier output terminal.   
     
     
         4 . The series regulator according to  claim 2 , wherein the level shifter includes an n-channel type seventh transistor disposed between a current source linked to a high-potential side power source, and a current source linked to a low-potential side power source,
 the seventh transistor has a drain connected to its own gate, and a source connected to the amplifier output terminal, and   a drain voltage of the seventh transistor makes the shift voltage.   
     
     
         5 . The series regulator according to  claim 3 , wherein the level shifter includes an n-channel type eighth current source transistor sharing a gate with the fifth load transistor, and linked to a low-potential side power source, a p-channel type ninth current source transistor sharing a gate with the sixth load transistor, and linked to a high-potential side power source, and an n-channel type seventh transistor disposed between the eighth and ninth current source transistors,
 the seventh transistor has a drain connected to its own gate, and a source connected to the amplifier output terminal, and   a drain voltage of the seventh transistor makes the shift voltage.   
     
     
         6 . The series regulator according to  claim 4 , wherein the source follower includes an n-channel type tenth transistor having a source connected to a current source linked to a low-potential side power source,
 the tenth transistor has a gate commonly connected with the gate of the seventh transistor, and   the source of the tenth transistor makes the follower output terminal.   
     
     
         7 . The series regulator according to  claim 5 , wherein the source follower includes an n-channel type eleventh current source transistor sharing a gate with the fifth load transistor, and linked to the low-potential side power source; and
 an n-channel type tenth transistor having a source connected to a drain of the eleventh current source transistor,   the tenth transistor has a gate commonly connected with the gate of the seventh transistor, and   the source of the tenth transistor makes the follower output terminal.   
     
     
         8 . The series regulator according to  claim 2 , wherein the level shifter includes a p-channel type twelfth transistor disposed between a current source linked to a high-potential side power source, and a current source linked to a low-potential side power source,
 the twelfth transistor has a drain connected to its own gate, and a source connected to the amplifier output terminal, and   a drain voltage of the twelfth transistor makes the shift voltage.   
     
     
         9 . The series regulator according to  claim 3 , wherein the level shifter includes an n-channel type eighth current source transistor sharing a gate with the fifth load transistor, and linked to a low-potential side power source,
 a p-channel type ninth current source transistor sharing a gate with the sixth load transistor, and linked to a high-potential side power source, and   a p-channel type twelfth transistor disposed between the eighth and ninth current source transistors,   the twelfth transistor has a drain connected to its own gate, and a source connected to the amplifier output terminal, and   a drain voltage of the twelfth transistor makes the shift voltage.   
     
     
         10 . The series regulator according to  claim 8 , wherein the source follower includes a p-channel type thirteenth transistor having a source connected to a current source linked to a high-potential side power source,
 the thirteenth transistor has a gate commonly connected with the gate of the twelfth transistor, and   the source of the thirteenth transistor makes the follower output terminal.   
     
     
         11 . The series regulator according to  claim 9 , wherein the source follower includes a p-channel type fourteenth current source transistor sharing a gate with the sixth load transistor, and linked to a high-potential side power source, and
 a p-channel type thirteenth transistor having a source connected to a drain of the fourteenth current source transistor,   the thirteenth transistor has a gate commonly connected with the gate of the twelfth transistor, and   the source of the thirteenth transistor makes the follower output terminal.   
     
     
         12 . The series regulator according to  claim 2 , wherein the level shifter includes an n-channel type fifteenth transistor and a p-channel type sixteenth transistor which are connected in series to each other through a source common thereto between a current source linked to a high-potential side power source and a current source linked to a low-potential side power source,
 the fifteenth transistor has a drain connected to its own gate,   the sixteenth transistor has a drain connected to its own gate,   the common source of the fifteenth and sixteenth transistors is connected to the amplifier output terminal, and   a drain voltage of each of the fifteenth and sixteenth transistors makes the shift voltage.   
     
     
         13 . The series regulator according to  claim 3 , wherein the level shifter includes an n-channel type eighth current source transistor sharing a gate with the fifth load transistor, and linked to a low-potential side power source,
 a p-channel type ninth current source transistor sharing a gate with the sixth load transistor, and linked to a high-potential side power source, and   an n-channel type fifteenth transistor and a p-channel type sixteenth transistor which are connected in series to each other through a source common thereto between the eighth and ninth current source transistors,   the fifteenth transistor has a drain connected to its own gate,   the sixteenth transistor has a drain connected to its own gate,   the common source of the fifteenth and sixteenth transistors is connected to the amplifier output terminal, and   a drain voltage of each of the fifteenth and sixteenth transistors makes the shift voltage.   
     
     
         14 . The series regulator according to  claim 12 , wherein the source follower includes an n-channel type seventeenth transistor and a p-channel type eighteenth transistor which are connected in series to each other through a source common thereto,
 the seventeenth transistor is connected to the gate of the fifteenth transistor,   the eighteenth transistor is connected to the gate of the sixteenth transistor, and   the common source of the seventeenth and eighteenth transistors makes the follower output terminal.   
     
     
         15 . The series regulator according to  claim 13 , wherein the source follower includes an n-channel type seventeenth transistor and a p-channel type eighteenth transistor which are connected in series to each other through a source common thereto,
 the seventeenth transistor is connected to the gate of the fifteenth transistor,   the eighteenth transistor is connected to the gate of the sixteenth transistor, and   the common source of the seventeenth and eighteenth transistors makes the follower output terminal.   
     
     
         16 . The series regulator according to  claim 1 , wherein the output transistor of the source follower includes a plurality of output transistors having a common gate,
 the plurality of output transistors receive the shift voltage from the level shifter at the common gate, and   a common source of the plurality of output transistors makes the follower output terminal.   
     
     
         17 . The series regulator according to  claim 1 , wherein a source voltage of a high-potential side power source of the differential amplifier and the level shifter is made higher than a source voltage of a high-potential side power source of the source follower. 
     
     
         18 . A semiconductor integrated circuit comprising:
 a logic circuit on a semiconductor substrate; and   a series regulator for supplying an operation power source to the logic circuit on the semiconductor substrate,   wherein the series regulator includes a differential amplifier, a level shifter including a level shift transistor with a drain connected to its own gate, and a source follower including an output transistor,   the differential amplifier includes an amplification stage having a non-inverting input terminal for inputting a reference voltage, an inverting input terminal for inputting a feedback voltage, and an amplifier output terminal,   the differential amplifier has a DC operation point at which an error of an output voltage at the amplifier output terminal to an input voltage to the non-inverting input terminal is equal to or less than a voltage between a gate and a source of an input transistor, and a follower output terminal of the source follower is feedback-connected to the inverting input terminal,   the level shifter accepts input of an output voltage from the amplifier output terminal at a source of the level shift transistor, and outputs a gate voltage thereof as a shift voltage,   the source follower receives the shift voltage from the level shifter at a gate of the output transistor, and a source of the output transistor makes the follower output terminal, and   a voltage at the follower output terminal makes the operation power source.   
     
     
         19 . The semiconductor integrated circuit according to  claim 18 , wherein the differential amplifier has a p-channel type first input transistor and an n-channel type second input transistor of which gates are commonly connected to the non-inverting input terminal,
 a p-channel type third input transistor and an n-channel type fourth input transistor of which gates are commonly connected to the inverting input terminal,   a first load connected to a drain of the first input transistor, and linked to a low-potential side power source, and   a second load connected to a drain of the second input transistor, and linked to a high-potential side power source, and   a common drain of the third and fourth feedback input transistors makes the amplifier output terminal.   
     
     
         20 . The semiconductor integrated circuit according to  claim 18 , wherein the output transistor of the source follower includes a plurality of output transistors having a common gate,
 the plurality of output transistors receive the shift voltage from the level shifter at the common gate, and   a common source of the plurality of output transistors makes the follower output terminal.